1. Navigate to Communications > eMail.
  2. Hover over the campaign name and select Manage.
  3. Click Receiver beside the specific mailing.
  4. In the popup, expand Contacts > Profile > Personal Info > Other.
  5. Click Special Flag to select it.
  6. Click Add.
  7. Add your Special Flag text.
  8. Click Preview to verify your results.
  9. Click Save.
  10. Click Done.